Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the annotations (readOnly=false, idempotent=true, destructive=false) it discloses essential behavior: no money is moved, nothing is sent to Fortnox, the change awaits human approval, and the response explains how the approved change is delivered. That is exactly the kind of context annotations cannot convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Short and front-loaded: purpose first, then the caveat that nothing is sent, then the body shape. The API path and docs URL are slightly noisy but arguably useful for an OpenAPI-derived tool.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With annotations present and an output schema existing, the description covers the safety profile, the human-approval flow, and the request body shape. Return value details are correctly left to the output schema; only the explicit sibling routing is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and there is only one parameter, but the schema only says 'object/array/string'; the description adds the actual body envelope ({"SupplierInvoicePayment": {…}}) and pinpoints the required field InvoiceNumber, which the schema does not declare. Genuine added value beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Create a supplier invoice payment') and immediately narrows scope: it records a payment already made, moves no money, and only proposes a change for approval. That distinguishes it clearly from the actual write/execute siblings and from the approval-oriented propose_* tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives clear context for when to use it ('records a payment that has already been made') and what it is not (it sends nothing to Fortnox), which implicitly routes the agent away from write-executing siblings. It does not explicitly name an alternative (e.g. execute_fortnox_write or propose_approve_supplier_invoice_for_payment), so it stops short of full when/when-not guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.